CN108988337B - Design method of energy storage device of micro-grid system and micro-grid system - Google Patents

Design method of energy storage device of micro-grid system and micro-grid system Download PDF

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CN108988337B
CN108988337B CN201810949084.1A CN201810949084A CN108988337B CN 108988337 B CN108988337 B CN 108988337B CN 201810949084 A CN201810949084 A CN 201810949084A CN 108988337 B CN108988337 B CN 108988337B
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battery pack
storage battery
power
energy
energy storage
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CN108988337A (en
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王威
王弦
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Changsha Victory Electricity Tech Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • H02J3/383—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

Abstract

The invention discloses a design method of an energy storage device of a micro-grid system and the micro-grid system, wherein the method comprises the following steps: analyzing the ratio of the energy storage energy of each group of storage battery pack to the total energy used by the energy storage device by utilizing a preset double storage battery pack energy storage device operation model based on a daily photovoltaic power generation output power curve in the microgrid system and a load demand power curve in a corresponding time period; based on the above, the number of the batteries required by each group of storage battery packs to meet the power balance condition in the first time interval and the second time interval is determined, and the optimal number of the series-connected batteries of each group of storage battery packs is obtained. The microgrid system comprises a load, a photovoltaic power generation device, a scheduling device and an energy storage device, wherein the scheduling device stores a preset running model of the energy storage devices of the double storage battery packs, and the energy storage devices are obtained according to the design method. The invention improves the use efficiency of the energy storage device in the microgrid system, prolongs the service life of the battery and slows down the aging condition of the battery.

Description

Design method of energy storage device of micro-grid system and micro-grid system
Technical Field
The invention relates to the technical field of micro-grid system control, in particular to a design method of a micro-grid system energy storage device and a micro-grid system.
Background
The photovoltaic island micro-grid balances power generation and load power with an electric energy storage device. Lead storage batteries continue to dominate the field due to economic considerations and technical maturity. Battery energy storage systems typically account for over 50% of the total investment in the system. In a solar island microgrid, a lead storage battery plays an important role in maintaining instantaneous power balance between power generation and power utilization, but the intermittency of solar energy causes a battery energy storage system to need charging and discharging operations in a short time, so that the battery can be prevented from being fully charged under certain conditions, lead sulfate is formed, the service efficiency of the battery is reduced, the service life of the battery is shortened, battery faults can be caused, the service life of the lead storage battery is generally short, and the long-term operation of the island microgrid is limited.
In the prior art, the use of a dispatchable power source (typically a diesel generator) to generate electricity would alleviate this problem, but would increase the operating costs of the system.
Disclosure of Invention
In order to solve the technical problem, the invention provides a design method of a micro-grid system energy storage device, which comprises the following steps: the method comprises the steps that firstly, based on a daily photovoltaic power generation output power curve and a load demand power curve in a corresponding time period in a microgrid system, the ratio of energy storage energy of each group of storage batteries to total energy used by an energy storage device is analyzed by using a preset double-storage-battery-pack energy storage device operation model, and corresponding use ratio parameters are obtained; and secondly, determining the number of the batteries of each group of storage batteries meeting the power balance condition in the first time interval and the second time interval according to the use ratio parameters of each group of storage batteries, and further obtaining the optimal number of the series-connected batteries of each group of storage batteries.
Preferably, the first step includes: recording and comparing the daily photovoltaic power generation output power curve in the microgrid system with the load demand power curve in the corresponding time period to obtain a power generation power and demand matching state curve in the corresponding time period; and based on the generated power and demand matching state curve, referring to the constraint condition of the energy storage device under the operating model of the double-storage-battery-pack energy storage device, carrying out demand probability analysis on the generated power and demand matching state curve, and determining the use ratio parameter of each group of storage batteries.
Preferably, the second step includes: according to the use ratio parameters of each group of storage battery packs, calculating a power value which reaches power balance in a first time interval, a power value which reaches power balance in a second time interval and an energy value which reaches energy balance in the second time interval which correspond to each group of storage battery packs under the condition that the use ratio parameters are met by the storage battery packs by using a preset probability model; and constructing a capacity configuration model of each group of storage battery packs, and calculating the number of batteries of each group of storage battery packs required for achieving power balance in a first time period and the number of batteries required for achieving power and energy balance in a second time period by using the daytime power balance power value, the nighttime power balance power value and the nighttime energy balance energy value corresponding to each group of storage battery packs to further obtain the optimal number of batteries of the corresponding storage battery packs.
Preferably, in the second step, the optimal number of series-connected cells of each group of the storage battery pack is determined by using the following expression:
SBKP＝max({SBKP_d，SBKP_n，SBKP_e})
SOP＝max({SOP_d，SOP_n，SOP_e})
wherein S isBKPIndicates the optimum number of series-connected cells of the first battery pack, SBKP_dIndicating the number of cells, S, required for the first battery pack to reach power balance during the first time periodBKP_nIndicating that the first battery pack has achieved work within the second period of timeNumber of cells required for rate balancing, SBKP_eIndicating the number of cells, S, required for the first battery pack to reach energy balance during the second period of timeOPIndicating the optimum number of cells in series in the second battery pack, SOP_dIndicating the number of cells, S, required for the second battery pack to reach power balance during the first period of timeOP_nIndicating the number of cells, S, required for the second battery pack to reach power balance during the second time periodOP_eIndicating the number of cells required for the second battery pack to reach energy balance during the second time period.
Preferably, in the second step, the number of cells required for the first battery pack to reach power balance in the first period and the number of cells required for the first battery pack to reach power and energy balance in the second period are calculated by using the following expressions:
Figure BDA0001771024630000021
Figure BDA0001771024630000022
Figure BDA0001771024630000023
wherein, CrateDenotes the charge/discharge time, χ, of the battery referencethd1Representing the daytime power balance value, C, of the first battery packNIndicating nominal capacity, P, of the batterybat1Indicating the number of parallel strings in the first battery pack, UbatIndicating the nominal voltage, S, of the cellBKP_dIndicates the number of cells, χ, required for the first battery pack to reach power balance during the first periodthn1Represents the night power balance power value of the first battery pack, SBKP_nIndicates the number of cells, χ, required for the first battery pack to reach power balance during the second periodthe1Indicating the nighttime energy balance energy value, S, of the first battery packBKP_eIndicates the first battery pack isNumber of batteries, SOC, required to reach energy balance in the second periodminRepresenting the minimum normalized state of charge, ε, of the batterybatRepresenting the coulombic efficiency of the cell.
Preferably, in the second step, the number of cells required for the second battery pack to reach power balance in the first period and the number of cells required for the second battery pack to reach power and energy balance in the second period are calculated by using the following expressions:
Figure BDA0001771024630000031
Figure BDA0001771024630000032
Figure BDA0001771024630000033
wherein, CrateDenotes the charge/discharge time, χ, of the battery referencethd2Represents the daytime power balance power value, C, of the second battery packNIndicating nominal capacity, P, of the cellbat2Indicating the number of parallel strings, U, in the second battery packbatIndicating the nominal voltage, S, of the cellOP_dIndicates the number of cells, χ, required for the second battery pack to reach power balance during the first periodthn2Represents the night power balance power value of the second battery pack, SOP_nIndicates the number of cells, χ, required for the second battery pack to reach power balance during the second period of timethe2Represents the nighttime energy balance energy value, S, of the second battery packOP_eIndicating the number of cells, SOC, required for the second battery pack to reach energy balance during the second periodminRepresents the minimum normalized state of charge of the battery, εbatRepresenting the coulombic efficiency of the cell.
Preferably, in the step one, the priority use standard, the charge/discharge start working state standard and the protection standard of the first/second storage battery pack in the first time period and the second time period are set based on the periodic equalizing charge principle of the first/second storage battery pack in the energy storage device, and the double-storage-battery-pack energy storage device operation model with the aim of minimizing the use of the generator in the microgrid system is constructed.
On the other hand, the invention also provides a micro-grid system, which comprises: a load; a photovoltaic power generation device; the scheduling device stores a preset double-storage-battery-pack energy storage device operation model and controls charging and discharging of the energy storage device according to the double-storage-pack energy storage device operation model; the energy storage device obtained by the design method comprises a first storage battery pack and a second storage battery pack, wherein the first storage battery pack is used for controlling the photovoltaic power generation device to store electric quantity for the first storage battery pack under the condition that the scheduling device determines that the generated energy of the photovoltaic power generation device meets the load requirement, and the second storage battery pack is used for meeting the power balance requirement and the voltage regulation requirement of the microgrid system under the control of the scheduling device.
Preferably, the scheduling device is connected to the load, the photovoltaic power generation device, the first storage battery pack and the second storage battery pack, wherein the scheduling device is configured to acquire corresponding real-time state information fed back by the load, the photovoltaic power generation device, the first storage battery pack and the second storage battery pack, and send a working state control instruction matched with the operating model of the energy storage device of the double storage battery packs to the photovoltaic power generation device, the first storage battery pack and the second storage battery pack respectively by using a preset operating model of the energy storage device of the double storage battery packs, so as to meet daily instantaneous power balance of the microgrid system.
Preferably, the scheduling device includes a scheduling analysis module, where the scheduling analysis module is configured to obtain a current charge state parameter of the first storage battery pack by analyzing real-time state information of the first storage battery pack, and further send an effective charge state control instruction to the first storage battery pack by using a preset maximum value of the charge state parameter of the first storage battery pack, when it is determined that the current charge state parameter of the first storage battery pack is lower than the maximum value of the charge state parameter of the first storage battery pack, until the current charge state parameter of the first storage battery pack is higher than or equal to the maximum value of the charge state parameter of the first storage battery pack.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the invention provides a design method of an energy storage device of a micro-grid system and a novel micro-grid system. According to the design method, the batteries in the energy storage device are designed in a grouping mode through power demand analysis of the daily micro-grid system, so that daily power demand pressure is relieved, and the service life of the storage battery is prolonged. Furthermore, a novel micro-grid system is constructed by utilizing the designed energy storage device with a double-storage-battery structure, the system limits the battery to operate in a complete-cycle charging and discharging mode, and the starting and operating conditions of the charging/discharging working state of each group of storage battery packs are set so as to achieve the purpose of protecting the energy storage battery. Under the condition of adding the second storage battery pack, the change of the output power of a part of photovoltaic power generation is absorbed, a smoother charging/discharging mode is provided for the first storage battery pack, and the huge change of charging and discharging current is avoided, so that the phenomenon that the service life of the battery is shortened because the battery energy storage device needs to be charged and discharged in a short time due to intermittent power generation of the solar photovoltaic power generation device is relieved, the service efficiency of the energy storage device is improved, the service time of the battery is prolonged, and the aging condition of the battery is slowed down.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic diagram of an overall structure of a microgrid system according to an embodiment of the present application.
Fig. 2 is a step diagram of a method for designing the energy storage device 12 in the microgrid system according to an embodiment of the present application.
Fig. 3 is a specific flowchart of a method for designing the energy storage device 12 in the microgrid system according to an embodiment of the present application.
Fig. 4 is a comparison graph of a daily photovoltaic power generation output power curve and a load demand power curve of a corresponding period in the design method of the energy storage device 12 in the microgrid system according to the embodiment of the present application.
Fig. 5 is a schematic diagram of a generated power and demand matching state curve in a design method of the energy storage device 12 in the microgrid system according to the embodiment of the present application.
Fig. 6 is a schematic diagram of an application of the energy storage device 12 in the entire microgrid system, which is obtained without using the method for designing the microgrid system energy storage device 12 according to the embodiment of the present application.
Fig. 7 is a schematic diagram of an application of the energy storage device 12 in the entire microgrid system, which is obtained by using the method for designing the energy storage device 12 in the microgrid system according to the embodiment of the present application.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
In a solar island microgrid, a lead storage battery plays an important role in maintaining instantaneous power balance between power generation and power utilization, but the intermittency of solar energy causes a battery energy storage system to need charging and discharging operations in a short time, so that the battery can be prevented from being fully charged under certain conditions, lead sulfate is formed, the service efficiency of the battery is reduced, the service life of the battery is shortened, battery faults can be caused, the service life of the lead storage battery is generally short, and the long-term operation of the island microgrid is limited. The prior art can alleviate this problem by using a schedulable power supply (typically a diesel generator) to generate electricity, but this will increase the operating cost of the system.
The invention therefore proposes an energy storage device for use in a microgrid system comprising a plurality of groups of storage batteries and a method for designing the same. The energy storage device divides a plurality of storage batteries in the energy storage device into a first storage battery pack (also called a main battery pack) and a second storage battery pack (also called a secondary battery pack) according to capacity, each storage battery pack comprises a plurality of parallel-connected battery strings, and each battery string comprises a plurality of storage batteries which are sequentially connected in series. Furthermore, the first storage battery pack is used as a main battery pack, has larger capacity and is responsible for storing energy when solar energy is sufficient or meets load requirements according to optimal strategy scheduling; the second battery pack is used as a secondary battery pack, has lower capacity and is used for meeting the daily instantaneous power balance requirement and the microgrid voltage regulation requirement. The energy storage device formed by adopting the mode of respectively carrying out charge and discharge scheduling control by configuring the double storage battery packs aims to relieve the operation pressure of the battery packs, particularly the first battery pack, and the following analysis requirements are met: 1) and (3) circulating operation: the first battery pack should preferentially perform full cycle operation and avoid incomplete operation; 2) reducing the average time to full charge: the first/second storage battery pack adopts a circulating operation and periodic equalizing charge mechanism, so that the average time between full charges is obviously reduced; 3) smooth charge/discharge process: the second storage battery pack is used for absorbing the change of photovoltaic power generation, so that the charging power curve of the first storage battery pack is smoother, a smoother charging mode is provided for the first storage battery pack, and the huge change of charging/discharging current is avoided.
It should be noted that, the above-mentioned complete cycle operation, also called complete charge and discharge operation, for the first storage battery pack means that, under the daily operation condition of the microgrid system, the cells in the first storage battery pack need to be operated to the preset minimum value of the state of charge parameter of the first storage battery pack (where the minimum value of the state of charge parameter of the first storage battery pack is in the range of 10% to 20%), then a charging power supply is plugged, and the charging is performed to a value higher than the maximum value of the state of charge parameter of the first storage battery pack (where the maximum value of the state of charge parameter of the first storage battery pack is in the range of 90% to 100%, preferably 100%), and the charging is regarded as one complete cycle charging. In the same way, the first battery pack also needs to be subjected to a full-cycle discharge operation. Complete charge and discharge is an important link for battery maintenance, and complete charge and discharge is recommended every time the battery is charged and discharged. Wherein, if the battery is not used much, it is recommended to perform full charge and discharge once a month. In addition, the periodic equalizing charge mechanism is to periodically equalize the charge of the first/second battery pack, which aims to equalize the battery characteristics, and means that the terminal voltage between the batteries is unbalanced due to individual differences, temperature differences and the like of the batteries during the use of the battery pack, and in order to avoid the deterioration of the unbalanced trend, the charging voltage of the battery pack is periodically increased, and the batteries are activated and charged. Wherein the period of the equalizing charge is typically once per month.
Fig. 1 is a schematic diagram of an overall structure of a microgrid system according to an embodiment of the application. As shown in fig. 1, the microgrid system includes at least: the system comprises a photovoltaic power generation device 11, an energy storage device 12, a generator device 13, a scheduling device 14 and a load 15. The dispatching device 14 is connected with the photovoltaic power generation device 11, the energy storage device 12 and the generator device 13 which can be used for supplying power to the load 15. In the embodiment of the present application, the energy storage device 12 includes a first battery pack 121 and a second battery pack 122, which are respectively connected to the scheduling device 14 and independently controlled by the scheduling device 14. Specifically, the first storage battery set 121 is used for controlling the photovoltaic power generation device 11 to charge the first storage battery set 121 through the scheduling device 14 to achieve the purpose of storing electric quantity under the condition that the scheduling device 14 determines that the electric quantity generated by the photovoltaic power generation device 11 meets the load requirement. The second battery pack 122 is used for matching with the first battery pack 121 under the control of the scheduling device 14 to meet the power balance requirement and the voltage regulation requirement of the microgrid system, so as to achieve the purpose of protecting the first battery pack 121, thereby prolonging the service life of the whole energy storage device 12. The generator device 13 is used for controlling the generator device 13 to supply power to the load 15 through the dispatching device 14 in the case that the dispatching device 14 determines that the photovoltaic power generation device 11 and the energy storage device 12 are not enough to meet the load requirement.
In addition, the scheduling device 14 can obtain corresponding real-time state information fed back by the load 15, the generator device 13, the photovoltaic power generation device 11, the first storage battery pack 121 and the second storage battery pack 122, and sends working state control instructions matched with the operation models of the two storage battery packs to the photovoltaic power generation device 11, the first storage battery pack 121 and the second storage battery pack 122 respectively by using a preset operation model of the two storage battery packs, so that daily instantaneous power balance of the microgrid system is met. The operation model of the energy storage device with the double storage battery packs is an implementation model for performing charge and discharge scheduling control on the double storage battery packs respectively, the requirement condition of specific charge and discharge operation conditions for prolonging the service life of the storage battery in the energy storage device 12 is analyzed further according to the defects of the prior art, the power balance requirement of the whole microgrid system is met, and the obtained corresponding operation rule of the energy storage device 12 is presented by a mathematical model.
Further, the operation model of the dual battery pack energy storage device is stored in the scheduling device 14. The operating model of the energy storage device with the double storage battery packs is constructed by a highest priority principle of a periodic equalizing charging mode and setting a priority use standard, a charging/discharging starting working state standard and a protection standard for the first storage battery pack and the second storage battery pack in a first time interval and a second time interval. In order to guarantee the principle of complete charging and discharging of the energy storage device 12, the model has the control principle of minimizing the use target of the generator device 13 in the microgrid system. Note that, in this example, the first period refers to a daytime period in which the solar photovoltaic power generation power is relatively sufficient, for example: 6 am to 6 pm. In addition, in this example, the second period refers to a nighttime period in which the solar photovoltaic power generation power is insufficient, for example: afternoon 6 hours to 6 am. The specific time of the first time interval and the second time interval is not limited in the invention, and the specific time of the first time interval and the second time interval can be set by a person skilled in the art according to factors such as the location of the microgrid system, seasons, sunshine time and the like.
In addition, the highest priority rule means that the first/second storage battery pack needs to perform a periodic equalizing charge operation according to a preset equalizing charge frequency, in this example, the equalizing charge frequency is once a month, the frequency parameter is set in the scheduling device 14, and a scheduling analysis module (described below) in the scheduling device 14 sends a corresponding equalizing charge instruction to the first/second storage battery pack at regular time. Furthermore, the scheduling analysis module can obtain data such as current charging state parameters, current charging power, residual capacity and the like of the first/second storage battery pack by analyzing the real-time state information of the first/second storage battery pack, judge whether the first/second storage battery pack is in a periodic equalizing charging mode or not, if so, and continuously sending an effective equalizing charge instruction to the first storage battery pack and the second storage battery pack which are in the periodic equalizing charge mode until the current charge state parameters of the first storage battery pack and the second storage battery pack are judged to be respectively higher than the maximum value of the charge state parameters of the corresponding first storage battery pack and the maximum value of the charge state parameters of the second storage battery pack (wherein the maximum value of the charge state parameters of the first storage battery pack ranges from 90% to 100%), so as to judge that the first storage battery pack and the second storage battery pack are in a full charge state. In this way, the highest priority principle (the principle of periodic equalizing charge of the first/second battery pack) in the above-described operating model of the dual battery pack energy storage device is realized: if the first/second battery pack is periodically equalized, the first/second battery pack must be fully charged.
Further, the scheduling device 14 includes a scheduling analysis module (not shown). The scheduling analysis module can analyze the acquired corresponding real-time state information fed back by the load 15, the generator device 13, the photovoltaic power generation device 11, the first storage battery pack 121 and the second storage battery pack 122 to obtain a corresponding analysis result: the power demand information of the load 15 at the current time, the power generation output power information of the photovoltaic power generation apparatus 11 at the current time, the first state of charge information of the first battery pack 121 at the current time, the second state of charge information of the second battery pack 122 at the current time, and the like. The first/second state of charge information includes at least a charge value (charge amount, remaining charge amount), a state of charge parameter (SOC), charge/discharge power, and the like for the first/second battery pack. Then, according to the analysis result, whether the current time is in the first time interval or the second time interval, whether the starting condition of the first/second storage battery pack is met, whether the first/second storage battery pack is in a full charge state, whether the first/second storage battery pack is in a charging state or a discharging state, whether the first/second storage battery pack is in a periodic balanced charging state, whether the generated power of the photovoltaic power generation device 11 meets the current load demand power, and the like are judged, and a corresponding working state control instruction is generated so as to control the charging or discharging state of the first/second storage battery pack and regulate and control the power supply state of the generator device 13.
Further, the scheduling analysis module sends an effective discharge state control instruction to the second storage battery pack 122 when determining that the current time is in the first time period, so as to control the second storage battery pack 122 to preferentially supply power to the load 15. In one embodiment, in the case that it is determined that the current time is in the first period and the generated power of the photovoltaic power generation apparatus 11 meets the current load demand power, the schedule analysis module sends an effective discharging state control instruction to the second battery pack 122 and sends an ineffective discharging state control instruction to the first battery pack 121, so as to control the second battery pack 122 to preferentially supply power to the load.
Further, the scheduling analysis module sends an effective discharge state control instruction to the first storage battery pack 121 when determining that the current time is in the second time period, so as to control the first storage battery pack 121 to preferentially supply power to the load 15 (rule three). In one embodiment, when determining that the current time is in the second time period, the scheduling analysis module sends an effective discharge state control instruction to the first storage battery pack 121 and sends an ineffective discharge state control instruction to the second storage battery pack 122 to control the second storage battery pack 122 to preferentially supply power to the load, so that the purpose that the second storage battery pack 122 meets the voltage regulation requirement of the entire microgrid system is achieved.
In this way, the preferential use standard of the first/second storage battery pack in the operation model of the double storage battery pack energy storage device in the first period and the second period is realized: in the first time period, the second battery pack 122 preferentially starts a discharging working state to supply power to the load (rule two); and in the second period, first battery pack 121 preferentially starts the discharge operation state to supply power to the load (rule three).
Further, the scheduling analysis module may obtain a current electric quantity value of the second battery pack 122 by analyzing the real-time status information of the second battery pack 122, and further, by using a minimum electric quantity allowable value stored in the scheduling analysis module for the second battery pack 122, when it is determined that the current electric quantity value of the second battery pack 122 is lower than or equal to the minimum electric quantity allowable value and the current time is within the first time period, an invalid discharge status control instruction is sent to the second battery pack 122, so as to achieve the purpose of prohibiting the second battery pack 122 from starting a discharge operating status to supply power to the load (rule four). Further, when it is determined that the current electric quantity value of second battery pack 122 is higher than the minimum electric quantity allowable value and the current time is in the first time period, according to the current power demand of the microgrid system, if second battery pack 122 is required to supply power to load 15, an effective discharge state control command is sent to second battery pack 122. Thus, the dual battery pack energy storage device operational model sets the criteria for the second battery pack 122 to initiate the charge/discharge operating state accordingly.
Further, the scheduling analysis module may obtain parameters, such as the required power of the corresponding load 15 at the current time, the generated output power of the photovoltaic power generation apparatus 11 at the current time, and the charging/discharging power of the second storage battery 122 at the current time, by analyzing the real-time status information of the load 15, the photovoltaic power generation apparatus 11, and the second storage battery 122, so as to determine whether the generated output power of the photovoltaic power generation apparatus 11 and the discharging power of the second storage battery 122 satisfy the current load power requirement. If the current time is in the first time period, an effective discharge state control instruction needs to be sent to the first storage battery pack 121 and the second storage battery pack 122 at the same time to control the first storage battery pack 121 to be put into use under the condition, so that the first storage battery pack 121, the second storage battery pack 122 and the photovoltaic power generation device 11 supply power to the load 15 at the same time (rule five).
In the rule five, the scheduling analysis module further needs to analyze the real-time status information of the first storage battery pack 121 to obtain the current charge status parameter of the first storage battery pack 121, and further cannot send an effective discharge status control instruction to the first storage battery pack 121 when determining that the current charge status parameter of the first storage battery pack 121 is lower than the maximum value of the charge status parameter for the first storage battery pack 121 stored in the scheduling analysis module, and determining that the current first storage battery pack 121 is not in the full charge status. That is to say, neither the photovoltaic power generation apparatus 11 nor the second battery pack 122 can meet the current load power demand, and under the condition that the current first battery pack 121 is not in the full-power state, the first battery pack 121 cannot be controlled to be put into power generation, and a corresponding operating state control instruction can be further sent to the generator apparatus 13, so as to achieve the purpose of meeting the power demand of the whole microgrid system.
Further, the scheduling analysis module may obtain the current charging state parameter of the first storage battery pack 121 by analyzing the real-time state information of the first storage battery pack 121, and further, when it is determined that the current charging state parameter of the first storage battery pack 121 is lower than the maximum value of the charging state parameter of the first storage battery pack 121 stored in the scheduling analysis module, continue to send an effective charging state control instruction to the first storage battery pack 121 until the current charging state parameter of the first storage battery pack 121 is higher than or equal to the maximum value of the charging state parameter. Thus, the dual battery pack energy storage device operation model sets a corresponding standard for starting and maintaining the charging working state for the first battery pack 121, so as to realize the function that the main battery pack 121 needs to adopt complete cycle operation in daily operation of the microgrid system.
In this way, the charge/discharge start working state standard of the first/second storage battery pack in the double storage battery pack energy storage device operation model in the first time interval and the second time interval is realized: in the first time period, if the current electric quantity value of second battery pack 122 is lower than or equal to the preset minimum electric quantity allowable value of second battery pack 122, the starting of the discharging operation state is prohibited (rule four); and in a first time period, if the photovoltaic power generation power in the microgrid system and the discharge power of the second storage battery pack 122 cannot meet the current load power demand, the first storage battery pack 121 starts a discharge working state to cooperate with the second storage battery pack 122 and the photovoltaic power generation device 11 to simultaneously supply power to the load (rule five, this rule takes precedence over rule six described below); and if the current charge state parameter of the first battery pack 121 is lower than the preset maximum value of the charge state parameter of the first battery pack 121, starting the charge working state until the current charge state parameter of the first battery pack 121 is higher than or equal to the maximum value of the charge state parameter thereof (rule six).
Further, the scheduling analysis module may obtain the current charging state parameter of the first storage battery pack 121 by analyzing the real-time state information of the first storage battery pack 121, and then determine whether the current charging state parameter of the first storage battery pack is equal to or less than the minimum charging state parameter value by using a preset charging state parameter threshold (including a maximum charging state parameter value and a minimum charging state parameter value) for the first storage battery pack stored in the scheduling analysis module. If so, a valid discharge state control command is sent to first battery pack 121 and an invalid charge state control command is sent to control first battery pack 121 to discharge only in this case, so that first battery pack 121 supplies power to load 15 simultaneously with second battery pack 122 and photovoltaic power generation device 11 (rule seven, which takes precedence over rule eight described below). In this way, the dual battery pack energy storage device operation model sets the protection standard for starting the discharge operation state when the first battery pack 121 is lower than a certain threshold, and at the same time, the protection standard (one of) of the first/second battery packs in the dual battery pack energy storage device operation model in the first time period and the second time period is realized: if the current charge state parameter of the first battery pack 121 is equal to or less than the preset minimum charge state parameter of the first battery pack 121, the first battery pack 121 starts a discharge operation state and cuts off the charge operation state, so as to achieve the purpose of discharging only under such a condition.
Furthermore, the scheduling analysis module can also send an effective charging state control instruction to the first storage battery pack and the second storage battery pack simultaneously under the condition that the current time is determined to be in the first time interval, so that the effective utilization of solar energy is ensured. In this way, the protection standard (one of) of the first/second storage battery pack in the operation model of the double storage battery pack energy storage device in the first period and the second period is realized: and in the first period, the first/second storage battery packs start charging working states at the same time.
Further, the scheduling analysis module can simultaneously start the charging operating states of the first and second storage battery packs when determining that the current time is in the first time period, and at this time, if it is determined that the current charging state parameter of the first storage battery pack 121 is less than or equal to the minimum charging state parameter of the first storage battery pack 121, send an effective charging state control instruction to the second storage battery pack 122, and send an invalid charging state control instruction to the first storage battery pack 121 (rule eight). In this way, the protection standard (one of) of the first/second storage battery pack in the operation model of the double storage battery pack energy storage device in the first period and the second period is realized: if the current charge state parameter of first battery pack 121 is equal to or smaller than the preset minimum value of the charge state parameter of first battery pack 121, second battery pack 122 starts the charge operation state, and first battery pack 121 cuts off the charge operation state, in which case only second battery pack 122 is charged.
The rules of the operating model of the double-storage-battery-pack energy storage device ensure the service life of the first storage battery pack 121, and can reduce the operating and maintaining cost of the island microgrid. In practical applications, the above rules may be translated into mathematical optimization problems as follows for the purpose of presenting a minimized usage of the generator device 13. Here, the use cost of the generator device 13 is expressed by the following expression:
Figure BDA0001771024630000111
wherein Y represents the minimum use cost of the generator device 13 in a certain period of time, F0Representing the fuel curve intercept factor, F, of the generator unit 131Representing the slope of the generator fuel curve, PgenRepresenting the rated power, P, of the generator unit 13D,tRepresents the output power of the generator device 13 at time t, t represents the operating time of the microgrid system, piDIndicating the fuel price. As can be seen from equation (1), if the minimum cost of using the generator device 13 is determined, the output power P of the generator device is requiredD,tAnd (4) limiting, wherein the limiting conditions (constraint conditions) are model expressions matched with the operating model of the double-battery-pack energy storage device, so that a mathematical model of the operating model of the double-battery-pack energy storage device is constructed. Further, the model is applied to the energy storage device 12 for operation limitation, so that the energy storage device 12 provides a power balance constraint condition matched with the operation model of the energy storage device of the double storage battery pack for the microgrid system, and the power balance constraint condition of the first/second storage battery pack in the fully-cycled operation state and the power balance condition of the generator device in the above model are represented by the following expressions:
Figure BDA0001771024630000112
Figure BDA0001771024630000121
in the formula IB1C,tThe charging current value of the first storage battery pack 121 at the time t is represented, and the parameter can be obtained by analyzing the acquired real-time state information of the first storage battery pack 121 through a scheduling analysis module; i isB2C,tThe parameter represents the charging current value of the second storage battery pack 122 at the time t, and the parameter can be obtained by analyzing the acquired real-time state information of the second storage battery pack 122 through the scheduling analysis module；
Figure BDA0001771024630000122
A reference current representing charging of first battery pack 121;
Figure BDA0001771024630000123
a reference current representing charging of second battery pack 122;
Figure BDA0001771024630000124
represents the maximum allowable charging current of first battery pack 121;
Figure BDA0001771024630000125
represents the maximum allowable charging current of second battery pack 122;
Figure BDA0001771024630000126
representing the maximum power of the generator means 13.
Further, the power demand balance condition of the entire microgrid system is expressed by the following expression in the periodic state of charge and not in the periodic state of charge of the energy storage device 12:
when β is 1, (1-2 α) | PB1,t|+PB2,t+αPPV,t+PD,t＝PLoad,t (5)
When beta is 0, PPV,t+PD,t-PB1,t-PB2,t＝PLoad,t (6)
Wherein β is a binary variable indicating whether the charge state is being periodically equalized, and is 1 if the charge state is being periodically equalized, or is 0 if the charge state is not periodically equalized; alpha is a binary variable, which indicates whether the photovoltaic power generation device 11 is in an available state, if so, the value is 1, otherwise, the value is 0; pB1,tThe charge/discharge power of the first storage battery pack 121 at the time t is represented, and the parameter can be obtained by analyzing the acquired real-time state information of the first storage battery pack 121 through a scheduling analysis module; pB2,tRepresents the charging/discharging power of second battery pack 122 at time t, and this parameter can be analyzed by the schedule analysis module for the second battery pack 122 acquired by the schedule analysis moduleObtaining real-time state information; pPV，tThe output power of the photovoltaic power generation device 11 at the time t can be obtained by analyzing the acquired real-time state information of the photovoltaic power generation device 11 through the scheduling analysis module; pLoad，tRepresenting the load demand power at time t.
Further, the constraint conditions of the charge/discharge state of the first battery pack 121 at the full-cycle operation in the power generation state and the non-power generation state of the photovoltaic power generation device 11 (that is, the photovoltaic power generation device 11 is in the power generation state for the first period of time and in the non-power generation state for the second period of time) are expressed by the following expressions:
when α is 1, α SOCB1,t≥αSOCB1,t-1 (7)
(1-alpha) SOC when alpha is 0B1,t≥(1-α)SOCB1,t-1 (8)
Therein, SOCB1,tA parameter indicating the state of charge of first battery pack 121 at time t; SOCB1,t-1Indicating the state of charge parameter of first battery pack 121 at time t-1. As can be seen from the above equations (7) and (8), the scheduling device 14 according to the present invention needs to monitor the current charge state parameter of the first storage battery pack 121 in real time, so that the first storage battery pack 121 can perform the discharging operation only when reaching the full charge state, thereby achieving the function of ensuring that the first storage battery pack 121 performs the complete charging and discharging.
On the other hand, according to the construction and implementation process of the above-mentioned dual battery pack energy storage device operation model, the present invention provides a design method of the energy storage device 12 under various constraints considering the dual battery pack energy storage device operation model, so as to determine the optimal number of cells required by the first battery pack 121 and the second battery pack 122 in the energy storage device 12.
Fig. 2 is a step diagram of a method for designing the energy storage device 12 in the microgrid system according to an embodiment of the present application. Fig. 3 is a specific flowchart of a method for designing the energy storage device 12 in the microgrid system according to an embodiment of the present application. The method for designing the energy storage device 12 will be described in detail with reference to fig. 2 and 3.
As shown in fig. 2 and 3, in step S210, based on a daily photovoltaic power generation output power curve in the microgrid system and a load demand power curve in a corresponding time period, a preset double-battery-pack energy storage device operation model is used to analyze a ratio of energy storage energy of each group of battery packs to total energy usage of the energy storage devices, so as to obtain a corresponding usage ratio parameter. That is to say, the probability density function of the energy storage capacity requirement of each group of storage battery packs needs to be analyzed, and the corresponding cumulative distribution function is further derived through integration, so that the probability distribution of the energy storage capacity requirement of each group of storage battery packs is obtained, and the use ratio parameter of each group of storage battery packs is obtained.
Specifically, firstly, an original daily photovoltaic power generation output power curve (a related curve obtained in daily operation under the condition that the operation model of the energy storage device of the double storage battery pack is not considered in the current microgrid system) in the microgrid system and a load demand power curve in a corresponding period are recorded, and the two curves are compared by means of difference values to obtain a generated power and demand matching state curve in the corresponding period.
In one embodiment, taking the original configuration and operation mode of a certain microgrid system as an example, the current microgrid system comprises: a photovoltaic array installation of 25kW, a diesel generator installation of 40kW, and 1 energy storage installation (battery pack) consisting of 60 storage batteries of 1200Ah cells. According to an original operation mode, the power generation power of the microgrid system for 11 days and the load demand power of the microgrid system for 11 days are recorded, a corresponding daily photovoltaic power generation output power curve and a load demand power curve of a corresponding time period are obtained, a figure 4 is referred, and the two curves are compared by using a formula (9) at the same time to obtain a power generation power and demand matching state curve. Fig. 4 is a comparison diagram of a daily photovoltaic power generation output power curve and a load demand power curve in a corresponding time period in the design method of the energy storage device 12 in the microgrid system according to the embodiment of the present application. In addition, formula (9) is expressed by the following expression:
Pmis,t＝PPV,t-PLoad,t (9)
in the formula, Pmis,tRepresents t timeThe generated power at the moment is matched with the state value of the demand. At Pmis,tWhen the output power is less than 0, it is indicated that the output power of the photovoltaic power generation device 11 cannot meet the load demand at the time t, and at this time, the generated energy of the original microgrid system and the load demand are in a mismatch state. The mismatch state information includes a power mismatch time and a mismatch power value corresponding to the mismatch time.
Fig. 5 is a schematic diagram of a generated power and demand matching state curve in a design method of the energy storage device 12 in the microgrid system according to the embodiment of the present application. As shown in FIG. 5, the ordinate of the graph shows the generated power and the demand matching state value P as shown in FIG. 5mis,t。
Next, as shown in fig. 2, based on the generated power and demand matching state curve, referring to the constraint condition of the energy storage device 12 under the dual-battery-pack energy storage device operation model, and using a preset probability model, performing demand probability analysis (kernel density estimation analysis) on the generated power and demand matching state curve to obtain usage ratio parameters of each group of battery packs (first/second battery packs) in the energy storage device 12, that is, determining probability distribution of energy storage capacity demand of each group of battery packs.
Specifically, the generated power and demand matching state curve shown in fig. 5 is divided into two samples of a first time period (day time period) and a second time period (night time period), and by fully referring to the constraint condition (mathematical model corresponding to the model) of the energy storage device 12 under the dual-storage-battery-pack energy storage device operation model, it is analyzed that the energy storage device 12 shows different patterns during day and night while maintaining the power balance function in the entire original microgrid system, and the patterns specifically include: daytime power balance mode, nighttime power balance mode, and nighttime energy balance mode. Further, a kernel function probability model (shown in formula 10) in the prior art is used to perform kernel density estimation analysis on the generated power and demand matching state curve in the different modes. Wherein the formula (10) is expressed by the following expression:
Figure BDA0001771024630000141
wherein n represents the number of samples, χiDenotes the ith sample, i denotes the sample number, khRepresenting a kernel function, h representing a time interval,
Figure BDA0001771024630000142
representing the kernel function probability density. Specifically, the probability density of each sample sampling value in different modes is calculated by using the formula (10), and then the probability density function is subjected to integration processing to obtain a result corresponding to the cumulative distribution function, wherein the result of the cumulative distribution function indicates that the microgrid system needs power and/or energy supplemented by the energy storage device 12 in time periods in which the different modes are located. Further, by using the above embodiment of the original configuration and operation mode of a certain microgrid system, referring to the operation model of the energy storage device with two storage battery packs, and then combining the actual use experience, that is, analyzing the probability distribution of the energy storage energy capacity requirement of each storage battery pack, so as to obtain the ratio of the energy storage energy of the first/second storage battery packs to the total energy used by the energy storage device (the total energy used by the energy storage device means that the power and/or energy required to be supplemented when the energy storage device 12 is used to balance the power of the entire microgrid system in the first/second time periods) and obtain the corresponding use ratio parameter. In this example, the capacity of the first battery pack 121 should be designed to meet at least 90% of the demand of the energy storage device 12 (i.e., the probability cumulative distribution is greater than or equal to 90%). The second battery pack satisfies 8% of the remaining demand (i.e., the probability cumulative distribution is greater than or equal to 8%). The remaining 2% of the demand is supplemented by the generator means 13.
Next, referring to fig. 2 and fig. 3 again, in step S220, according to the usage ratio parameter of each group of storage battery packs (the probability distribution of the energy storage capacity requirement of each group of storage battery packs), the number of cells required by each group of storage battery packs to satisfy the power balance condition in the first time period and the second time period is determined, and further, the optimal number of cells connected in series in each group of storage battery packs is obtained.
Specifically, first, according to the obtained usage rate parameter of each group of storage battery packs, a probability model is used to calculate a power value for achieving power balance in a first time period, a power value for achieving power balance in a second time period, and an energy value for achieving energy balance in the second time period, which correspond to each group of storage battery packs when the corresponding usage rate parameter is satisfied. Further, the capacity of the first battery pack accounts for 90% of the total demand of the energy storage device 12 (i.e., the probability cumulative distribution is greater than or equal to 90%), and the power and energy values in the corresponding time periods (different samples) obtained from fig. 4 and 5 are substituted into the result corresponding to the cumulative distribution function, so as to obtain the power value of the first battery pack that reaches power balance in the first time period, the power value that reaches power balance in the second time period, and the energy value that reaches energy balance in the second time period. Similarly, the capacity of the second battery pack accounts for 8% of the total demand of the energy storage device 12 (i.e., the probability cumulative distribution is greater than or equal to 8%), and the power and energy values in the corresponding time periods (different samples) obtained from fig. 4 and 5 are substituted into the result corresponding to the cumulative distribution function, so as to obtain the power value of the second battery pack that reaches power balance in the first time period, the power value that reaches power balance in the second time period, and the energy parameter that reaches energy balance in the second time period.
And then, constructing a capacity configuration model of each group of storage battery packs, and calculating the number of batteries required by each group of storage battery packs to achieve power balance in a first time period and the number of batteries required by each group of storage battery packs to achieve power and energy balance in a second time period by using the daytime power balance value, the nighttime power balance value and the nighttime energy balance value corresponding to each group of storage battery packs, so as to further obtain the optimal number of batteries connected in series with the corresponding storage battery packs.
Wherein a capacity allocation model of the first secondary battery pack is expressed using the following expressions, the model including a calculation expression of the number of cells required for the first secondary battery pack to achieve power balance in the first period of time (expression 11), a calculation expression of the number of cells required for the first secondary battery pack to achieve power balance in the second period of time (expression 12), a calculation expression of the number of cells required for the first secondary battery pack to achieve energy balance in the second period of time (expression 13), and a calculation expression of the optimum number of cells connected in series to the first secondary battery pack (expression 14), respectively:
Figure BDA0001771024630000151
Figure BDA0001771024630000152
Figure BDA0001771024630000153
SBKP＝max({SBKP_d，SBKP_n，SBKP_e}) (14)
wherein, CrateReference current, χ, representing battery charge/dischargethd1Representing the daytime power balance value, C, of the first battery packNIndicating nominal capacity, P, of the batterybat1Indicating the number of parallel strings in the first battery pack, UbatIndicating the nominal voltage, S, of the cellBKP_dIndicates the number of cells, χ, required for the first battery pack to reach power balance during the first periodthn1Represents the night power balance power value of the first battery pack, SBKP_nIndicates the number of cells, χ, required for the first battery pack to reach power balance during the second periodthe1Indicating the nighttime energy balance energy value, S, of the first battery packBKP_eIndicating the number of cells, SOC, required for the first battery pack to reach energy balance during the second periodminRepresenting the minimum normalized state of charge, ε, of the batterybatRepresenting the coulombic efficiency of the cell (typically, the coulombic efficiency equals 90%), SBKPIndicating the optimum number of series connected cells of the first battery pack.
Also, a capacity allocation model of the second battery pack is expressed by expressions including an expression (expression 15) for calculating the number of cells required for the second battery pack to achieve power balance in the second period, an expression (expression 16) for calculating the number of cells required for the second battery pack to achieve power balance in the second period, an expression (expression 17) for calculating the number of cells required for the second battery pack to achieve energy balance in the second period, and an expression (expression 18) for calculating the optimum number of cells connected in series to the second battery pack:
Figure BDA0001771024630000161
Figure BDA0001771024630000162
Figure BDA0001771024630000163
SOP＝max({SOP_d，SOP_n，SOP_e}) (18)
wherein, χthd2Representing the daytime power balance power value, P, of the second battery packbat2Representing the number of parallel strings, S, in the second battery packOP_dIndicates the number of cells, χ, required for the second battery pack to reach power balance during the first periodthn2Represents the night power balance power value of the second battery pack, SOP_nIndicates the number of cells, χ, required for the second battery pack to reach power balance during the second period of timethe2Indicating the nighttime energy balance energy value, S, of the second battery packOP_eIndicating the number of cells, S, required for the second battery pack to reach energy balance during the second period of timeOPIndicating the optimum number of cells in series in the second battery pack.
In this example, in the embodiment in which the original configuration and operation mode of the certain microgrid system are calculated according to the capacity configuration model of the first battery pack, the first battery pack is composed of 46 cells. In the embodiment of calculating the original configuration and operation mode of a certain microgrid system according to the capacity configuration model of the second storage battery pack, the second storage battery pack is composed of 14 batteries.
Fig. 6 is a schematic diagram of an application of the energy storage device 12 in the entire microgrid system, which is obtained without using the method for designing the microgrid system energy storage device 12 according to the embodiment of the present application. Fig. 7 is a schematic diagram of an application of the energy storage device 12 in the entire microgrid system, which is obtained by using the method for designing the energy storage device 12 in the microgrid system according to the embodiment of the present application. Fig. 6 shows a power consumption curve, a single cell voltage change curve, a single cell state of charge change curve, and a single cell current change curve for an energy storage device prior to use in a microgrid system including an energy storage device having a dual battery configuration in accordance with the present invention. In this case, the expected service life of the battery energy storage device (60 cells) was determined to be 2.45 years by the Schiffer method. Fig. 7 shows a power consumption curve, a single cell voltage variation curve, a single cell charge state variation curve and a single cell current variation curve of the energy storage device 12 after the microgrid system including the energy storage device having a double-battery-pack structure according to the present invention is operated under the same power generation condition and load condition and the energy storage device 12 is controlled according to the scheduling device 14 according to a preset double-battery-pack energy storage device operation model. The advantages of the novel battery energy storage device are directly reflected in the service life of the whole energy storage device, and the expected service life of the first storage battery pack and the second storage battery pack is 4.12 years and 2.60 years respectively. It should be noted that the Schiffer method is a model for evaluating the life cycle of a battery, and the model can compare the effects of different operating conditions, different system scales and different battery technologies on the life of the battery.
The invention provides a design method of an energy storage device of a micro-grid system and a novel micro-grid system. The design method comprises the steps of determining the use ratio of each storage battery to the total energy storage device by analyzing the probability analysis result of the daily photovoltaic power generation output power curve of the original microgrid system and the load demand power curve in the corresponding time period and referring to a preset double-storage-battery-pack energy storage device operation model, and further obtaining the optimal number of each storage battery pack, so that the design of the energy storage device is completed. Therefore, batteries in the energy storage device are designed in a grouping mode through power demand analysis of the daily micro-grid system, daily power demand pressure is relieved, and the service life of the storage battery is prolonged.
Furthermore, a novel micro-grid system is constructed by utilizing the designed energy storage device with a double-storage-battery structure, the system utilizes a scheduling device to respectively control the first storage battery pack/the second storage battery pack according to a preset double-storage-battery-pack energy storage device operation model, the batteries are limited to operate in a complete-cycle charging and discharging mode, and starting and operating conditions of charging/discharging working states of each group of storage battery packs are set so as to achieve the purpose of protecting the energy storage batteries. Under the condition of adding the second storage battery pack, the change of the output power of a part of photovoltaic power generation is absorbed, a smoother charging/discharging mode is provided for the first storage battery pack, and the huge change of charging and discharging current is avoided, so that the phenomenon that the service life of the battery is shortened because the battery energy storage device needs to be charged and discharged in a short time due to intermittent power generation of the solar photovoltaic power generation device is relieved, the purpose of protecting the first storage battery pack is achieved, the service efficiency of the energy storage device is further improved, the service life of the battery is prolonged, and the aging condition of the battery is slowed down.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (8)

1. A method for designing an energy storage device of a microgrid system comprises the following steps:
the method comprises the steps that firstly, based on a daily photovoltaic power generation output power curve in a micro-grid system and a load demand power curve in a corresponding time period, the ratio of energy storage energy of each group of storage batteries to total energy use of the energy storage devices is analyzed by utilizing a preset double-storage-battery-pack energy storage device operation model, and corresponding use ratio parameters are obtained;
step two, according to the use ratio parameter of each group of storage battery pack, determining the number of batteries required by each group of storage battery pack to meet the power balance condition in a first time interval and a second time interval, and further obtaining the optimal number of series-connected batteries of each group of storage battery pack, wherein the step two comprises the following steps:
according to the use ratio parameters of each group of storage battery packs, calculating a power value which reaches power balance in a first time interval, a power value which reaches power balance in a second time interval and an energy value which reaches energy balance in the second time interval which correspond to each group of storage battery packs under the condition that the use ratio parameters are met by the storage battery packs by using a preset probability model;
the method comprises the following steps of constructing a capacity configuration model of each group of storage battery packs, calculating the number of batteries required by each group of storage battery packs to reach power balance in a first time period and the number of batteries required by each group of storage battery packs to reach power and energy balance in a second time period by utilizing a daytime power balance power value, a nighttime power balance power value and a nighttime energy balance energy value corresponding to each group of storage battery packs, and further obtaining the optimal number of batteries of the corresponding storage battery packs, wherein the number of the batteries required by the first storage battery pack to reach power balance in the first time period and the number of the batteries required by each group of storage battery packs to reach power and energy balance in the second time period are calculated by utilizing the following expressions:
Figure FDA0003254610150000011
Figure FDA0003254610150000012
Figure FDA0003254610150000013
wherein, CrateDenotes the charge/discharge time, χ, of the battery referencethd1Representing the daytime power balance value, C, of the first battery packNIndicating nominal capacity, P, of the batterybat1Indicating the number of parallel strings in the first battery pack, UbatIndicating the nominal voltage, S, of the cellBKP_dIndicates the number of cells, χ, required for the first battery pack to reach power balance during the first periodthn1Represents the night power balance power value of the first battery pack, SBKP_nIndicates the number of cells, χ, required for the first battery pack to reach power balance during the second periodthe1Indicating the nighttime energy balance energy value, S, of the first battery packBKP_eIndicating the number of cells, SOC, required for the first battery pack to reach energy balance during the second time periodminRepresenting the minimum normalized state of charge, ε, of the batterybatRepresenting the coulombic efficiency of the cell.
2. The design method according to claim 1, wherein the first step comprises:
recording and comparing the daily photovoltaic power generation output power curve in the microgrid system with the load demand power curve in the corresponding time period to obtain a power generation power and demand matching state curve in the corresponding time period;
and based on the generated power and demand matching state curve, referring to the constraint condition of the energy storage device under the operating model of the double-storage-battery-pack energy storage device, carrying out demand probability analysis on the generated power and demand matching state curve, and determining the use ratio parameter of each group of storage batteries.
3. The design method according to claim 1, wherein in the second step, the optimal number of series-connected cells of each group of the battery packs is determined by using the following expression:
SBKP＝max({SBKP_d，SBKP_n，SBKP_e})
SOP＝max({SOP_d，SOP_n，SOP_e})
wherein S isBKPIndicates the optimum number of series-connected cells of the first battery pack, SBKP_dIndicating the number of cells, S, required for the first battery pack to reach power balance during the first time periodBKP_nIndicating that the first battery pack has reached within the second period of timeNumber of cells required for power balance, SBKP_eRepresenting the number of cells, S, required for the first battery pack to reach energy balance during the second time periodOPRepresents the optimum number of series-connected cells of the second group of battery packs, SOP_dIndicating the number of cells, S, required for the second battery pack to reach power balance during the first period of timeOP_nIndicating the number of cells, S, required for the second battery pack to reach power balance during the second time periodOP_eIndicating the number of cells required for the second battery pack to reach energy balance during the second time period.
4. The design method according to claim 1 or 3, wherein in the second step, the number of cells required for the second battery pack to reach power balance in the first period and the number of cells required for the second battery pack to reach power and energy balance in the second period are calculated by using the following expressions:
Figure FDA0003254610150000021
Figure FDA0003254610150000022
Figure FDA0003254610150000023
wherein, CrateDenotes the charge/discharge time, χ, of the battery referencethd2Representing the daytime power balance value, C, of the second battery packNIndicating nominal capacity, P, of the cellbat2Indicating the number of parallel strings, U, in the second battery packbatIndicating the nominal voltage, S, of the cellOP_dIndicates the number of cells, χ, required for the second battery pack to reach power balance during the first periodthn2Represents the night power balance power value of the second battery pack, SOP_nIndicating that the second battery pack has reached within the second period of timeNumber of cells, χ, required for power balancethe2Indicating the nighttime energy balance energy value, S, of the second battery packOP_eIndicating the number of cells, SOC, required for the second battery pack to reach energy balance during the second time periodminRepresenting the minimum normalized state of charge, ε, of the batterybatRepresenting the coulombic efficiency of the cell.
5. The design method according to claim 1, wherein in the step one, the preferential use standard, the charge/discharge start-up working state standard and the protection standard of the first/second storage battery pack in the first period and the second period are set based on the periodic equalizing charge principle of the first/second storage battery pack in the energy storage device, and the double storage battery pack energy storage device operation model with the aim of minimizing the use of the generator in the microgrid system is constructed.
6. A microgrid system comprising:
a load;
a photovoltaic power generation device;
the scheduling device stores a preset double-storage-battery-pack energy storage device operation model and controls charging and discharging of the energy storage device according to the double-storage-pack energy storage device operation model;
the energy storage device obtained according to the design method of any one of claims 1 to 5, comprising a first storage battery pack and a second storage battery pack, wherein the first storage battery pack is used for controlling the photovoltaic power generation device to store electric quantity for the first storage battery pack under the condition that the power generation amount of the photovoltaic power generation device is determined to meet the load requirement through the scheduling device, and the second storage battery pack is used for meeting the power balance requirement and the voltage regulation requirement of the microgrid system under the control of the scheduling device.
7. The system of claim 6, wherein said scheduling device is coupled to said load, said photovoltaic power generation device, said first battery pack, and said second battery pack, wherein,
the scheduling device is configured to acquire corresponding real-time state information fed back by the load, the photovoltaic power generation device, the first storage battery pack and the second storage battery pack, and send working state control instructions matched with the running models of the energy storage devices of the two storage battery packs to the photovoltaic power generation device, the first storage battery pack and the second storage battery pack respectively by using a preset running model of the energy storage devices of the two storage battery packs so as to meet daily instantaneous power balance of the microgrid system.
8. The system of claim 6 or 7, wherein the scheduling apparatus comprises a schedule analysis module, wherein the schedule analysis module is configured to obtain the current state of charge parameter of the first battery pack by analyzing the real-time status information of the first battery pack,
and further utilizing a preset maximum value of the charge state parameter of the first storage battery pack, and sending an effective charge state control instruction to the first storage battery pack under the condition that the current charge state parameter of the first storage battery pack is judged to be lower than the maximum value of the charge state parameter of the first storage battery pack until the current charge state parameter of the first storage battery pack is higher than or equal to the maximum value of the charge state parameter of the first storage battery pack.
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